My b2evolution Version: 4.1.x

I am getting the following error when submitting new posts.

--
Pinging b2evolution.net...
Remote error: Invalid return payload: enable debugging to examine incoming payload (XML error: junk after document element at line 2, column 0) (2)
--

Now, I think I enabled debugging (couldn't find documentation on how to) and I got this:

---SENDING---
POST /evonetsrv/xmlrpc.php HTTP/1.0
User-Agent: XML-RPC for PHP 2.2.2
Host: rpc.b2evo.net:80
Accept-Encoding: gzip, deflate
Accept-Charset: UTF-8,ISO-8859-1,US-ASCII
Content-Type: text/xml; charset=ISO-8859-1
Content-Length: 616

<?xml version="1.0" encoding="ISO-8859-1" ?>
<methodCall>
<methodName>b2evo.ping</methodName>
<params>
<param>
<value><string>5</string></value>
</param>
<param>
<value><string>http://www.coolmanchester.com/</string></value>
</param>
<param>
<value><string>b2evo</string></value>
</param>
<param>
<value><string>Cool Manchester</string></value>
</param>
<param>
<value><string>http://www.coolmanchester.com/index.php/CM/</string></value>
</param>
<param>
<value><string>en-GB</string></value>
</param>
<param>
<value><string>Calling Participants for Manchester Pride</string></value>
</param>
</params>
</methodCall>
---END---
---GOT---
HTTP/1.1 200 OK
Date: Wed, 04 Apr 2012 12:48:03 GMT
Server: Apache/2.2.9 (Debian) PHP/5.2.6-1+lenny13 with Suhosin-Patch mod_ssl/2.2.9 OpenSSL/0.9.8g
X-Powered-By: PHP/5.2.6-1+lenny13
Vary: Accept-Encoding,User-Agent
Content-Encoding: gzip
Content-Length: 144
Connection: close
Content-Type: text/html

‹-Ž±
1D{¿bKm\8!„4‚ß ‰Y/I6lâÅÏ÷ÂÙÍÌ›ÑNÍA;s·ÍF Î(€›Ã'{z/™<$j=<¨V;SUj¦öLw<Á’a#aàDè&Z9SÃÞ;î²ÊŠß¥¼Î%”±œ!nèQ»\§éýÑz$Æ©™
---END---
HEADER: date: Wed, 04 Apr 2012 12:48:03 GMT
HEADER: server: Apache/2.2.9 (Debian) PHP/5.2.6-1+lenny13 with Suhosin-Patch mod_ssl/2.2.9 OpenSSL/0.9.8g
HEADER: x-powered-by: PHP/5.2.6-1+lenny13
HEADER: vary: Accept-Encoding,User-Agent
HEADER: content-encoding: gzip
HEADER: content-length: 144
HEADER: connection: close
HEADER: content-type: text/html
---INFLATED RESPONSE---[153 chars]---
<br />
<b>Fatal error</b>:  Call to undefined method Messages::get_messages() in <b>/home/b2evonet/www/evonetsrv/xmlrpc.php</b> on line <b>372</b><br />

---END---

Any ideas?